The present invention relates to generator stator core ventilation ducts and, more particularly, to ventilation duct spacer posts inserted between magnetic laminations of a generator stator core.
During normal generator operation, heat is generated in the copper conductors and the steel core due to the copper and steel losses. To ensure generator reliable performance, the generated heat must be removed efficiently. Conventionally, heat is removed from copper conductors to the steel core, which is cooled by forced-convection flows (air or hydrogen gas), through ventilation ducts between steel laminates, radial stator ducts, and the rotor-stator annular gap.
Generator stator cores are constructed by stacking many layers of magnetic laminations. The ventilation ducts may be inserted between groups of layers by including spacers such as rails into the core stack, which allow for the passage of cooling gas through the core during operation. These spacers must be positioned in such a way to assure tightness of the core during assembly and operation. Additionally, they must not block or restrict the flow of gas through the stator, which would result in temperatures exceeding normal operating temperatures, thereby reducing efficiency. These spacers are subjected to the same magnetic field as the magnetic core and must not introduce excessive heat loss.
Spacers for ventilation ducts between generator stator core magnetic laminations should be configured to assure core tightness while maximizing the ventilation duct cross section so as not to block or restrict the flow of gas through the stator and while minimizing magnetic loss in the spacers. As a consequence, the life of the generator can be extended while increasing operating efficiency, and thereby increasing generator output rating.
In an exemplary embodiment the invention, a ventilation duct in a generator stator core having a core axis and including a plurality of layers of magnetic laminations is defined by spacer posts disposed between groups of the magnetic laminations. The spacer posts are secured with longitudinal axes thereof substantially parallel to the core axis. The spacer posts may be press fit with at least one of the magnetic laminations and may be formed of a non-magnetic alloy or carbon steel. In a preferred arrangement, the spacer posts are arranged in triangle arrays or staggered rows or the like. Preferably, the spacer posts have a cylindrical shape. In one embodiment, the spacer posts are secured to the tooth tip corners of the magnetic laminations. The ventilation duct may further be defined by radially oriented rails disposed between the groups of the magnetic laminations. In this context, the spacer posts are secured to the tooth tip corners.
In another exemplary embodiment of the invention, a generator stator core having a core axis includes a plurality of layers of magnetic laminations, and a plurality of ventilation ducts defined by spacer posts disposed between groups of the magnetic laminations. The spacer posts are secured with longitudinal axes thereof substantially parallel to the core axis.